Elevators typically include a car that moves vertically through a hoistway between different levels of a building. At each level or landing, a set of hoistway doors are arranged to close off the hoistway when the elevator car is not at that landing. The hoistway doors open with doors on the car to allow access to or from the elevator car when it is at the landing. It is necessary to have the hoistway doors coupled appropriately with the car doors to open or close them.
Conventional arrangements include a door interlock that typically integrates several functions into a single device. The interlocks lock the hoistway doors, sense that the hoistway doors are locked and couple the hoistway doors to the car doors for opening purposes. While such integration of multiple functions provides lower material costs, there are significant design challenges presented by conventional arrangements. For example, the locking and sensing functions must be precise to satisfy codes. The coupling function, on the other hand, requires a significant amount of tolerance to accommodate variations in the position of the car doors relative to the hoistway doors. While these functions are typically integrated into a single device, their design implications are usually competing with each other.
Conventional door couplers include a vane on the car door and a pair of rollers on a hoistway door. The vane must be received between the rollers so that the hoistway door moves with the car door in two opposing directions (i.e., opening and closing). Common problems associated with such conventional arrangements is that the alignment between the car door vane and the hoistway door rollers must be precisely controlled. This introduces labor and expense during the installation process. Further, any future misalignment results in maintenance requests or call backs.
It is believed that elevator door system components account for approximately 50% of elevator maintenance requests and 30% of callbacks. Almost half of the callbacks due to a door system malfunction are related to one of the interlock functions.
There is a need in the industry for an improved arrangement that provides a reliable coupling between the car doors and hoistway doors, yet avoids the complexities of conventional arrangements and provides a more reliable arrangement that has reduced need for maintenance. One proposal has been to replace mechanical components with electromagnetic components. Examples are shown in U.S. Pat. Nos. 6,070,700; 5,174,417 and 1,344,430.
Implementing electromagnetic elevator door coupler devices is not without challenges. For example, residual current within an electromagnet's coil after the electromagnet has been turned off can tend to keep an electromagnet and a coupled component such as a vane coupled together although separation is desired. There is also a competing concern between maintaining a sufficiently adequate coupling force while still allowing some relative vertical movement between magnetically coupled components to accommodate changes in elevator car position during loading or unloading at a landing, for example. It is also necessary to attempt to prevent an accumulation of ferrous debris on an active surface of an electromagnet.